In electronic mail services provided by carriers such as cellular phone companies, an Internet mail address, using the phone number (e.g. “09011112222”) of each subscriber as the account name and a name common to the carrier as the domain name is assigned to each subscriber as a default Internet mail address. Therefore, there exist some dealers or business entities generating destination addresses automatically by software by altering the phone number part of the Internet mail address sequentially or at random and sending messages (advertisement messages, etc.) to an indefinite number of subscribers by use of the generated destination addresses, by which large numbers of subscribers are receiving emails that are repeatedly sent from unfamiliar dealers, etc.
Such emails are of the type making the users feel troubled or annoyed. Electronic mails of the type include emails unilaterally sent to the users, such as the so-called spam mails, UCEs (Unsolicited Commercial Emails) and UBEs (Unsolicited Bulk Emails). Such emails making the users feel troubled or annoyed will hereinafter be called “undesirable emails” in this specification.
In cases where the carrier charges for email reception, each subscriber has to pay even when such undesirable emails are received. Further, in electronic mail services of cellular phones, etc., emails are generally delivered to the cellular phone, etc. one by one. Therefore, the subscriber is in formed of the mail reception on every email delivery from unfamiliar dealers and that is quite troublesome.
As a countermeasure against such undesirable emails, a service is being provided to the subscribers, in which each subscriber registers addresses or domain names for rejecting email reception, and email delivery from sources corresponding to the registered addresses or domain names is blocked. However, unless each subscriber registers the addresses or domain names for the delivery rejection by operating the cellular phone, etc., the delivery of undesirable emails can not be stopped. Thus, each subscriber has to register the delivery rejection addresses or domain names every time when undesirable emails start arriving and that is very troublesome to the subscribers.
In a technique disclosed in Japanese Patent Provisional Publication No. 2000-163341, an upper limit of the number of emails that can be received from the same email sender per day is set as a condition of email reception of each email user, by which reception of a large number of emails from the same email sender in a day is prevented.
The publication also discloses a technique for registering known (familiar) senders and restricting email reception from other senders.